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Immunology |
1 Department of Microbiology and Immunology, and 2 Sylvester Comprehensive Cancer Center, Miller School of Medicine, University of Miami, Florida
Requests for reprints: Diana M. Lopez, Department of Microbiology and Immunology, Miller School of Medicine, University of Miami, P.O. Box 016960 (R-138), Miami, FL 33101. Phone: 305-243-6632; Fax: 305-243-4409; E-mail: dlopez{at}med.miami.edu.
Key Words: MUC1 urokinase Stat1 tumor immunity
Expression of the transmembrane isoform of Mucin 1 (MUC1/TM) in an aggressive murine mammary tumor line, DA-3, does not alter tumor development and metastasis, leading to death of the host. However, tumor cells expressing a secreted isoform of MUC1 (MUC1/sec) fail to develop tumors in immunocompetent mice. The rejection of MUC1/sec-expressing tumor cells is immunologically mediated, as, initially, innate cells and, ultimately, T cells are required. After gene array analysis, and confirmation at the protein level, it was discovered that MUC1/sec-expressing tumor cells (DA-3/sec) have a significant reduction in expression of urokinase-type plasminogen activator (uPA) relative to the parental tumor line and tumor cells expressing MUC1/TM. The serine protease uPA has been found to be involved in growth-promoting signaling, angiogenesis, and induction of matrix remodeling leading to metastasis. Although the tumor-promoting Stat3 transcription factor was unaltered in these tumor cells, the tumor-suppressive and IFN-responsive signal transducer and activator of transcription 1 (Stat1) is dramatically up-regulated in DA-3/sec cells. In addition, treatment of various murine and human cell lines with conditioned medium containing MUC1/sec results in up-regulation of Stat1. DA-3/sec tumor cells are also sensitized to the antiproliferative effects of IFN-
. Furthermore, transfection of the Stat1 gene into DA-3 tumor cells leads to a down-regulation of uPA and delays tumor progression. Thus, Stat1 up-regulation in DA-3/sec cells seems to play a significant role in the mechanism(s) by which rejection of tumor cells expressing MUC1/sec may be occurring. [Cancer Res 2008;68(7):2427–35]
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